Wind energy can be converted in a windmill and used to produce mechanical work. A wind turbine uses that mechanical work to produce electricity by applying said work to rotate a generator. The efficiency of the device is the ratio between the energy produced by the device, and the wind energy that enters the device. To avoid significant energy loses, as much wind energy as possible must be converted to kinetic energy that contributes to the desirable movement of the device.
Many modern windmills and wind turbines comprise a vertical tower, attached to the ground, which provides a stable base for the device and elevates it up to a height where the velocity of the wind is suitable to operate the device. The velocity of the wind generally increases with elevation. The structure is exposed to the wind and can be damaged by it, if the wind is too powerful compared to the limitation of the material properties of the structure. The structure is exposed not only to the force of the wind, but also to other weather conditions, such as rain, lightning, storm, sunlight, humidity, etc.
Near the top of the tower there is a device suitable to be driven by the wind. In many cases, said device is a fan-like set of blades, wherein each blade is twisted for the purpose of being aerodynamically fit for smooth movement though the air. That device usually moves in a circular motion, by utilizing the wind and the aerodynamic shape of the surface. The circular motion occurs around an axis, connected to the top of the tower, and the plane in which the circular motion occurs is usually perpendicular to the ground, but can also be horizontal.
When the wind hits a surface which is at some distance from the central axis, a moment is created. The size of the moment is in direct proportion to the force produced by the wind and the distance between the central axis and the point where the wind hits the blades. To produce greater power, the blades need to be as long as possible, to create a large moment, but as the length of the blades grow, so does their weight, and a large velocity of wind is required to cause motion. On the other hand, if the wind is too strong the device can be damaged. To avoid such damage or low efficiency, the longest length for the blades is determined by the largest moment permitted on the device in order to avoid excessive abrasion or material fatigue, and the shortest length is usually determined by the amount of desired output.
It is an object of the present invention to provide a device and method that overcome the drawbacks of the prior art.
It is another object of the invention to provide a device that can be adjusted in order to exploit the wind power to its maximum, at any given time.
Other objects and advantages of the invention will become apparent as the description proceeds.